Control device



March 18, 1952 LARKIN 2,590,022

CONTROL DEVICE Filed Aug. 2, 1948 Fig).

T0 PUMP L 0A D Inventor: Thqmas E. Lab-kin,

b d. m

y His ttorney.

nated as droop, and the -;droop to the control, as ;of the decay of thisopposite control to zero is called dc-drooping.

is a view at section 2-2 of Fig. 1,

.. speed control resistance 21.

Patented Mar. 18, 1952 CONTROL DEVICE Thomas E. Larkin, Schenectady, N.Y., assignor to General Electric Company, a corporation of New YorkApplication August 2, 1948,v Serial No. 42,031

6 Claims.

,My invention relates to control systems for mechanical, or hydraulicelectric functions and, .more particularly, stabilizationand-regulation.

to such systems requiring object of my invention is to provide animproved, inexpensive, reliable stabilization control device formechanical, loontrolsystems.

hydraulic or electric My invention decreases the possibility ofhunttroduction of a stabilization signal, which then ;is,graduallyreduced to zero. This temporary reduction or recalibration forstabilization is desigprocess of applying drooping. The processPreviously, this effect has been obtained by variousmechanical,hydraulic and electronic d vices, but all have been more complicated andcostly than the present system.

For a better understanding of my invention,

;-reference is made to the accompanyin drawing ofa particular embodimentthereof in which Fig.

1 *a partly sectional schematic view and Fig. 2 looking in the directionof the arrows.

Referring to the drawing, piston l acts against 'thespring l' in thecylinder 2. The piston is actedupon bythe delivery pressure of ahydraulic :pump 3' through the tube 2". Piston rod 4 operates a brush 5over the resistance 6 of a potentiometer 1 in series connection with thefield of the-pump driving motor 3, directly controlling the speed ofoperation of the pump according to out- ;put pressure as a load functionof the pump. At the same time, the motion of the piston rod iscommunicated to the bar 8 parallel to the piston ,rod and rigidlyconnected to it by the link 9. Bar-:8 rigidly connects the free ends oftwo identical bellows l and II of an input bellows set, anchored at l2and I3. An output set of two identical bellows l4 and I is similarlyanchored at I6 and I! and similarly connected at their free ends by abar l8. Tubes l9 and 2!] connect corresponding pairs of bellows of thetwo sets and are interconnected by a tube 2| in which is a variablevalve 22. Movement of the bar I 8 is communicated by a pin 23 in the barl8 through a lever 24 pivoted at 25 to a brush 26 mounted on the lever24. This brush is operated over a reverse Adjustable springs 2 29 and 30biasthe lever 24 to a central position with the brush 26 centrallypositioned on 'the resistor 21 as indicated in Figure 1.

The springs 29 and 30 come to rest against stop 3i constructed andpositioned so as to provide positive centering of the lever 24.Individual adjusting screws 32 and 33 allow droop in the two directionsto be either equal or unequal. The springs 29 and 30 are preferably madeof a bimetal so that their tension will increase when the temperaturefalls to compensate for the increased viscosity of the oil in thesystem. The above described apparatus, including components numbered 23through 33 may be referred to below as a stabilization signal device.

Since operation of the control is reversible for the two directions ofpiston movement, the cycle of operation for but one direction of pistonmovement will be described. The piston I moving to the right carrieswith it the piston rod 4 and the brush 5 decreasing the seriesresistance in the shunt motor field, causing motor 3 to run slower. Thesame motion of the piston rod is communicated through the link 9 to thebar 8, compressing the bellows H and forcing oil through the tube 20 toexpand the bellows I5. At the same time, oil from bellows .I4 is forcedthrough tube 19 to expand the bellows ID. The resulting movement of thebar 18 is transmitted through the pin 23 and the lever 24 pivoted at 25to move the brush 26 to the right over the resistor 21 and by so doingincreases the series resistance in the field of the driving motor 3. Theamount of droop thus introduced can be made any desired percentage, suchas ten per cent, of the resistance change of the'potentiometer lmadeabove.

De-drooping is accomplished as follows: As the bar [8 moves-to the left,the lever 24 acts against the spring 30, which applies arestoring forceto the lever and hence to the bellows I5 forcing oil through therestricted duct provided by the valve 22 until the lever again occupiesits center position and the resistance of the resistor 27 isagain-returned to normal. The length of time to return the lever to zerois varied by the adjustments of the valve andthe biasing springs.

It will be seen that the magnitude of the deflectionof the lever 24 willbedependent not only upon the magnitude of the deflection of the bar 8,but also upon the speed of deflection of the bar 8. This is truebecause, if the bar 8 is deflected very slowly, the compression of thefluid in tube 2.0 due to the compression of the bellows M will becompletely accommodated by the passage of hydraulic fluid through .valve22 without requiring any deflection of lever 24 due to expansion ofbellows 15. If an intermediate speed of deflection of the bar 8 isobtained, the fluid compression due to compression of the bellows IIwill be only partially accommodated by the passage of hydraulic fluidthrough valve 22 and a small deflection of lever 24 will result, etc.

Bellows 34 communicating into the connecting tube I9 is a reservoir forvariations in oil volume due to temperature change. It is controlled bythe spring 35, which applies a pressure greater than that required tomove the brush 26.

My invention may be adapted for operation with hydraulic or mechanicalcontrols as well as with the electrical control disclosed above. It willbe understood that other modifications may be made without departingfrom the invention. The appended claims are therefore intended to coverany such modifications within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A control ssytem for a drive means connected to a variable load forvarying the speed of said drive means in response to variations in saidload, said system comprising a. control device movable in response tosaid load variations, hydraulic means responsive to movements of saidcontrol device to apply drooping and delayed de-drooping characteristicsto said system, said hydraulic means comprising a pair of input bellowsand a pair of output bellows, said bellows each having one fixed end andone free end, an input connector means interconnecting said free ends ofsaid input bellows and connected to said control device to be actuatedthereby, an output connector means interconnecting said free ends ofsaid output bellows, means providing intercommunication betweenassociated ones of said pairs of bellows to transmit motion from saidinput connector means to said output connector means, a memberconnecting said output connector and said control device for applying adrooping characteristic to said control system, means for biasing saidmember to a predetermined position, a connection between the interiorsof said output bellows to provide for the return of said member to saidpredetermined position in accordance with its bias and to apply a timedelayed de-drooping characteristic to said control system.

2. A control system for a drive means connected to a variable load forvarying the speed of said drive means in response to variations in saidload, said system comprisin a control device movable in response to saidload variations, hydraulic means responsive to movements of said controldevice to apply drooping and de-drooping characteristics to said system,said hydraulic means comprising a pair of input bellows and a pair ofoutput bellows, said bellows each having one fixed end and one free end,an input connector means interconnecting said free ends of said inputbellows and connected to said control device to be actuated thereby, anoutput connector means interconnecting said free ends of said outputbellows, means providing intercommunication between associated ones ofsaid pairs of bellows to transmit motion from said input connector meansto said output connector means, a speed droop control device, a pivotedoutput lever connected to said output connector means and engaging saidspeed droop control device to provide a drooping characteristic in 75 inaccordance with said control system, a restricted duct connectin theinteriors of said output bellows, a biasing means arranged to engagesaid output lever to provide opposing forces to movement thereof ineither direction, a stop means arranged to cooperate with said biasingmeans to positively center said lever, said biasing means tending torestore said lever to its center position with a time delay determinedby said restricted duct to de-droop said control system.

3. A control system for a drive means connected to a variable load forvarying the speed of said drive means in response to variations in saidload, said system comprising a control device movable in response tosaid load variations, hydraulic means responsive to movements of saidcontrol device to apply drooping and de-drooping characteristics to saidsystem, said hydraulic means comprising a pair of input bellows and apair of output bellows, said bellows each having one fixed end and onefree end, an input connector means interconnecting said free ends ofsaid input bellows and connected to said control device to be actuatedthereby, an output connector means interconnecting said free ends ofsaid output bellows, means providing intercommunication betweenassociated ones of said pairs of bellows to transmit motion from saidinput connector means to said output connector means, a speed droopcontrol device, a'pivoted output lever connected to said outputconnector means and engaging said speed droop control device to providea drooping characteristic in said control system,a duct connecting theinteriors of said output bellows, an adjustable valve in said duct,individually adjustable biasing springs arranged to engage said lever toprovide a restoring force to return said lever to a center position uponrotation of said lever from said center position by said outputconnector, and stop means positioned to cooperate with said springs andsaid lever to positively center said lever after a delay depending uponthe adjustment of said springs and said valve.

4. In a control system of the type having a control device positioned inaccordance with an operating condition of an apparatus to be controlled,a stabilization device comprising an input member connected to saidcontrol device for positioning thereby, a stabilization signal deviceadjustably spring biased to a predetermined central position forproviding a stabilization signal for said system in accordance with adeflection from said central position, a hydraulic.

coupling interconnectin said=input member and said signal device fordeflecting said signal device in accordance with the magnitude and speedof a change in position of said input member, said hydraulic couplingincluding a bypass valve for causing slippage of said hydraulic couplingunder the restoring force of the spring bias of said signal device tocause said signal device to return to said predetermined centralposition after a predetermined time interval dependent upon themagnitude of said deflection.

5. In a control system of the type having a control device positioned inaccordance with an operatin condition of an apparatus to be controlled,a stabilization device comprising an input member connected to saidcontrol device for positioning thereby, a' stabilization signal devicenormally adjustably spring biased. to a predetermined central positionbut connected to provide a stabilization signal for said system adeflection from said cantra-l position, a hydraulic couplinginterconnecting said input member and said signal. device for deflectingsaid signal device in accordance with the magnitude and speed of achange in position of said input member, said hydraulic couplingincluding a bypass valve for causing slippage of said hydraulic couplingunder the restorin force of the spring bias of said signal device tocause said signal device to return to said predetermined centralposition independent of the position of said input member after apredetermined time interval dependent upon the magnitude of saiddeflection.

6. A hydraulic stabilization device for an automatic positioning controlsystem comprising a v of mechanically interconnected bellows, hydraulicfirst pair of hydraulic bellows mechanically interconnected for movementin response to movements of a control member within the system to bestabilized, movement in a particular direction compressing one of saidbellows and expanding the other of said bellows, a second pair pair withone bellows of said second pair, said second pair of bellows beingbiased by spring devices to a predetermined centered position, a passageincluding an adjustablethrottling valve interconnecting said hydraulicducts, and a stabilization signal device connected for positioning inaccordance with the position of said second pair of bellows. I

THOMAS E. LARKIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

